In the prior art, it is often required to detect a thickness of a multilayer stacked plate in high accuracy. For example, the multilayer stacked plate may comprise a PTC (Positive Temperature Coefficient) material layer and two metal layers covered on both sides of the PTC material layer, respectively. Because the electrical and thermal properties of the multilayer stacked plate are closely related to its thickness, the thickness of the multilayer stacked plate must be detected in high accuracy. In order to detect the thickness of multilayer stacked plate with high accuracy, in the prior art, offline detection is usually used. In this case, before detecting, it is necessary to produce a multilayer stacked plate with sufficient length, and then to accurately detect the thickness of the multilayer stacked plate in an offline manner in the laboratory. If the difference between the thickness of the detected multilayer stacked plate and the preset thickness is larger than a preset value, it would have to discard the length of multilayer stacked plate, which will lead to considerable waste.